Long Term Evolution (LTE) network of 3G mobile communication comprises an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and an Evolved Packet Core (EPC) network. The E-UTRAN includes a set of Evolved NodeBs (eNBs). The EPC includes a Mobile Management Entity (MME) and a Serving Gateway (S-GW) etc., and therefore the network architecture is flat. The eNBs and the MME/S-GW are connected through S1 interface. The eNBs may be connected to each other through X2 interface. S1 interface and X2 interface are logical interfaces. A MME/S-GW can manage one or more eNBs, and an eNB can be controlled by a plurality of MMEs/S-GWs. In addition, an eNB can manage one or more cells. LTE advanced (LTE-A) system is evolved from the LTE system and has the same network architecture with the LTE. The difference between LTE-A and LTE is that some new technologies such as coordinated multi-point, spectrum aggregation and relay are applied to LTE-A to enhance the system performance.
In order to reduce costs of network construction and operation, the trend of the next generation mobile network is consequentially self-configuration, self-optimization, and less and less manual intervention. Therefore, the concept of self-organized network (SON) is introduced, which includes a mobility load balancing optimization (MLB) and a mobility robustness optimization (MRO) etc.
Such optimizations as the MLB and the MRO may result in modification of cell mobility parameter, thus a negotiation mechanism is required to coordinate the modification of the mobility parameter of two related adjacent cells between eNBs. The current negotiation process for mobility parameter modification consists of a request message, an acknowledgement message and a failure message. When a mobility parameter negotiation is required, the source base station where the source cell locates sends a mobility parameter modification request message to the target base station where the target cell locates. The mobility parameter modification request message comprises a cell ID of the source cell, a cell ID of the target cell, and the mobility parameter information of the source base station per se, the mobility parameter information which the target base station suggests modifying, and the cause of the mobility parameter negotiation, wherein a cell ID is the cell global identifier which can uniquely determine a cell. If the target base station modifies the parameter successfully, a mobility parameter modification acknowledgement message is returned. Otherwise, a mobility parameter modification failure message is returned. The mobility parameter modification failure message includes: a reason of failure, and a mobility parameter range which the target base station allows to be modified.
However, since the information (including the cell ID of the source cell and the cell ID of the target cell) of the negotiated cells pair is included only in the request message and is not included in the acknowledgement message and the failure message during the current negotiation process, it causes the following problems: when a plurality of service cells under the current source base station initiate a mobility parameter negotiation to the cells of other base stations, if the source base station receives acknowledgement/failure message from a plurality of target base stations/target cells, the source base station may not be able to recognize which source cell the mobility handover parameter negotiation is performed to. In addition, when the service cells of a source base station initiate in parallel mobility parameter negotiation processes for a plurality of target cells, the source base station may fail to know which target cell a negotiation message comes from via the address of the transport layer, and it may further fail to know which target cell the acknowledgement/failure message comes from. Consequently, the above problem will result in message disorder and finally result in inconsistency of mobility parameter modification between the cells pair, which causes cell mobility parameter modification error and degrade the network performance.